Our aim is to investigate the possible existence of regulatory systems in cells involving systematic and reversible modification of the properties of intracellular proteins by modification of their sulfhydryl-disulfide status. I have chosen to center much of our efforts on tubulin and mitotic regulation in general because of results in these areas which we have already obtained. The work takes a number of forms but much of it requires a detailed knowledge of tubulin S-D status and how it can be modified, and especially the effects of such modification on polymeization. Thus, I will begin with a set of projects concerning tubulin in vitro, extend this to tubulin in vivo, follow this with studies of enzymes and proteins such as glutathione reductase, thioredoxin and its reductase, etc., which may be involved in vivo regulation and then begin to generalize this to other proteins which may be part of a battery of proteins whose activity is regulated in concert with tubulin as a function of change in cell state. The project will use several species of marine eggs and also CHO cells in culture.